Traditionally, samples of J3 entomopathogenic nematodes which have been reared in large quantities are stored—for transportation or for future use—in containers which are aerated. Aeration is essential if the nematodes are to survive, for they require oxygen (air) to be able to respire properly. Hence, some storage containers have positive ventilation provided by holes in the top or side walls of the container, and other containers use a membrane, or a panel, of a material through which air can permeate, to provide the necessary oxygen to the nematodes.
Aeration, however, is only one of the requirements for successful long term storage of cryptobiotic J3 nematodes. Another requirement is that the water activity of the storage environment must be maintained at substantially the required (pre-determined) value.
If a fixed amount of water is provided in the container in which the nematodes are to be stored, the aeration of the container will result in some water loss from the storage environment. With long term storage, this loss of water from the container can reduce the water activity within the container, so that the nematodes begin to dry out. Further loss of water from the container results in further desiccation of the J3 nematodes, which affects them adversely, and can lead to their death.
Clearly, it will be advantageous to maintain the water activity in the storage environment at the preferred or required value for successful long term storage—and this is one of the objectives of the present invention.